The present invention relates to a method for displaying impending danger due to speed associated with the driving situation of a vehicle which is equipped with means for detecting a preceding vehicle in front and for recording the distance between the two vehicles and their speed relative to one another and which is also equipped with means for determining the current visual range.
With increasing traffic density, the increasing number of multiple collisions occurring between vehicles following one another (because of inadequate distance between them or excessive speed in poor visibility) emphasizes the requirement for a simple and reliable display of the impending danger associated with the driving situation of a vehicle. Up to now, there has been a lack of such a display which meets the specific perception requirements of mass traffic and which, therefore, satisfies an essential and fundamental precondition for a high level of acceptance in motorized traffic.
An object of the present invention is, therefore, to provide a method for displaying the impending danger due to speed associated with the driving situation of a vehicle and a display device for carrying out the method, which satisfy the previously mentioned precondition.
This and other objects are achieved by the present invention which provides a method for displaying the impending danger due to speed associated with a driving situation of a first vehicle which has a device that detects a second vehicle in front and measures a distance between the first and second vehicles and a speed of the first and second vehicles relative to one another and which also has a device that determines a current visual range. This method comprises the steps of recording the distance a.sub.m from the first vehicle to at least one of the second vehicle and an obstacle, the relative speed V.sub.rel between the first and second vehicles or between the first vehicle and an obstacle, the current visual range a.sub.sw, a speed of the first vehicle v.sub.eig, and a steering angle .beta..sub.L Of the first vehicle. A safety distance between the first vehicle and the second vehicle is determined and a first difference ##EQU1## where .tau.=reaction time of a first vehicle driver
b=deceleration of the first vehicle from v.sub.eig PA1 .beta..sub.L =steering angle PA1 b=deceleration of the second vehicle from v.sub.eig
is formed, where DELTA a is a measure with sign of the maintenance or non-maintenance of a non-dangerous following distance to the second vehicle or obstacle in front and the instantaneous speed v.sub.eig of the first vehicle, which can be increased or reduced. A maximum speed v.sub.sw which is still safe is determined as a function of the measured visual range a.sub.sw and a second difference ##EQU2## where .tau.=reaction time of the first vehicle driver PA0 is formed, where DELTA v is a measure with sign of an amount by which the speed of the first vehicle is less than or greater than a non-dangerous maximum speed of the first vehicle, which speed depends on the visual range a.sub.sw. The smaller or more negative of the current values of DELTA a and DELTA v is then selected, the selected value being the value more critical to safety. The selected current value is used for triggering and emitting a danger distance and impending danger display in such a way that this display indicates, in symbolic proportion, a degree of difference between both: the instantaneous speed of the first vehicle and a first vehicle speed which is currently still safe; and a current measure of danger or freedom from danger.
The objects are also achieved by an embodiment of the present invention which provides a display apparatus for displaying the impending danger due to speed associated with a driving situation of a first vehicle which has a device that detects a second vehicle in front and measures a distance between the first and second vehicles and a speed of the first and second vehicles relative to one another and which also has a device that determines a current visual range. The display device comprises a range scale which extends from an adequate, positive value to a dangerously small, negative value representing DELTA values of at least one of the differences between a measured driving condition and an instantaneously still safe driving condition, and a measured driving speed and an instantaneously still safe driving speed. This range scale has the shape of a threshold bar comprising two triangular areas touching at their apexes at a common contact point and rotated by 180 degrees relative to one another. A display symbol in the form of a mark is provided that is deflectable over the range scale as a function of a currently selected DELTA value. The common contact point of the triangular areas symbolizes the speed at which the vehicle can still be driven safely.
The method according to the invention is based on the fundamental idea of continuously defining, determining and calculating a degree of danger and displaying it to the driver of the vehicle and, in fact, independently of whether the driver is driving his vehicle as the following vehicle too close to the vehicle in front or to some other obstacle (distance problem) or is driving too fast in fog (visual range problem).
The signals necessary for this purpose are obtained from vehicle environment sensors, for example from a distance warning radar or distance recording radar and an infrared visual range measuring system, and are analyzed, together with vehicle condition signals, by a safety computer. On the basis of its specific programming, this computer determines and/or decides, for the respective current driving condition, which degree of danger is instantaneously predominant and indicates the respectively most dangerous condition on a display. In addition to this, cognitive information on the remoteness or nearness of a state of danger takes place by means of a continuous analog or quasi-analog display, which therefore reproduces the trends.
In particular, the distance a.sub.m to the vehicle in front or the obstacle and the relevant relative velocity v.sub.rel are determined by a radar sensor, a representative value for the instantaneous visual range a.sub.sw is determined by an infrared visual range measurement system, the vehicle's own speed v.sub.eig is determined by a vehicle speed pick-up and the steering angle .beta..sub.L is determined by a steering angle pick-up. From these values, a "difference from the safety distance" DELTA a, which is relevant to proximity, is determined as a function of the instantaneous distance a.sub.m, the vehicle's own speed v.sub.eig, the reaction time .tau. of the vehicle driver, the deceleration b of the vehicle and the steering angle .beta..sub.L. A "difference from the speed which is still safe" DELTA v, which is relevant to the visual range, is determined as a function of the visual range a.sub.sw as determined, the vehicle's own speed v.sub.eig, the reaction time .tau. of the vehicle driver and the deceleration b of the vehicle.
In a following step, the respectively smaller difference, i.e. the more critical one in terms of safety, is selected automatically from these two values without the knowledge of or action by the vehicle driver and supplied to the vehicle driver, in a further step, in a display.
In this, it is important that the vehicle driver should have no knowledge of whether the instantaneous display is the result of a distance analysis or a visual range measurement and analysis. The driver is therefore only informed of the extent of the instantaneous danger or lack of danger in his driving situation so that, by matching or reducing the speed, he can, in each of the two cases, bring the distance from danger, and the safety, to the necessary amount or he can increase it.
The display device, according to the invention, for carrying out the method has a display symbol in the form of a deflectable indicator or mark in any shape whatsoever (for example in the shape of a colored or illuminated bar, etc.), which symbol can be deflected over a range scale extending from an adequate, and to this extent positive, difference DELTA to one which is excessively, therefore dangerously small, and to this extent negative, relative to the speed which can still be instantaneously considered as just non-dangerous. The scale can be, for example, a very simple shape of two triangular areas touching at the apex and rotated by 180.degree., the contact point of the two areas marking the position of the display symbol for the non-dangerous maximum speed of the vehicle. These areas are preferably laid out with different signal colors in such a way that the display symbol is present or moves, when the non-dangerous maximum drivable speed is still not being used fully, in the region of a green triangular area, for example, and, in the case of an excessively high speed, and therefore one involving danger, it is present or moves in the region of a red triangular area.